I use Mobil 1 15w-50 available at Walmart in 5 qt containers- about $25. Often you have to look for the 15-50 stuff- it seems to sell out first.
I've had this stuff in my Valkyrie for 12,000 miles and it just seems like it beginning to get dirty. It'll look dark brown, but you can still see through it.
I used to use Lucas 20w-50 full synthetic until they raised the price to $9 a quart. It was actually even better- at about 10,000 miles, it looked about as dark as maybe tea, or thin coffee. At 15,000, it was beginning to get a dark color, like strong coffee, but was still thick when cold, and felt like it hadn't broken down at all.